User manual BENDIX R-8P PRESSURE EQUALIZING PILOTRELAY

[. . . ] As the piston begins to move downward it forces the inlet/exhaust valve off the inlet seat, allowing air from the reservoir to be delivered out the delivery ports of the R-8PTM valve in direct proportion to the pressure received at the service port. Any differential between service and delivery pressure caused by friction or resistance to the movement of the piston (commonly called crack pressure and normally in the range of 2 to 4 p. s. i. ) is eliminated due to passage of air through the orifice in the piston. SD-03-1061A 1 R-8PTM VALVE PISTON SPRING PISTON ORIFICE BRAKE VALVE R-8PTM VALVE PISTON SPRING BRAKE VALVE PISTON ORIFICE SERVICE SUPPLY SUPPLY SERVICE VENT RESERVOIR INLET/EXHAUST VALVE ASSEMBLY VENT RELAY VALVE SERVICE BRAKES RESERVOIR INLET/EXHAUST VALVE ASSEMBLY EXHAUST RELAY VALVE SERVICE BRAKES DELIVERY FIGURE 2 - OPERATIONAL VIEW OF APPLICATION DELIVERY FIGURE 3 - OPERATIONAL VIEW OF BALANCED POSITION R-8PTM VALVE PISTON BRAKE VALVE PISTON ORIFICE BALANCE (FIG. 3) The air pressure being delivered by the open inlet valve also is effective on the bottom area of the R-8PTM valve relay piston. When air pressure beneath the piston equals the service air pressure on top of the piston, the piston lifts slightly and the inlet/exhaust valve is returned to the inlet seat. [. . . ] PLEASE READ AND FOLLOW THESE INSTRUCTIONS TO AVOID PERSONAL INJURY OR DEATH: When working on or around a vehicle, the following general precautions should be observed at all times. Park the vehicle on a level surface, apply the parking brakes, and always block the wheels. Stop the engine and remove ignition key when working under or around the vehicle. When working in the engine compartment, the engine 6. 7. 8. should be shut off and the ignition key should be removed. Where circumstances require that the engine be in operation, EXTREME CAUTION should be used to prevent personal injury resulting from contact with moving, rotating, leaking, heated or electrically charged components. Do not attempt to install, remove, disassemble or assemble a component until you have read and thoroughly understand the recommended procedures. Use only the proper tools and observe all precautions pertaining to use of those tools. If the work is being performed on the vehicle's air brake system, or any auxiliary pressurized air systems, make certain to drain the air pressure from all reservoirs before beginning ANY work on the vehicle. If the vehicle is equipped with an AD-ISTM air dryer system or a dryer reservoir module, be sure to drain the purge reservoir. Following the vehicle manufacturer's recommended procedures, deactivate the electrical system in a manner that safely removes all electrical power from the vehicle. Never exceed manufacturer's recommended pressures. Never connect or disconnect a hose or line containing pressure; it may whip. Never remove a component or plug unless you are certain all system pressure has been depleted. Use only genuine Bendix ® replacement parts, components and kits. Replacement hardware, tubing, hose, fittings, etc. must be of equivalent size, type and strength as original equipment and be designed specifically for such applications and systems. 3 1 9 8 2 6 PISTON ORIFICE 3 SERVICE (CONTROL) PORT VENT SUPPLY PORT 4 10 5 11 12 DELIVERY PORTS EXHAUST 7 FIGURE 6 - CUTAWAY 9. Components with stripped threads or damaged parts should be replaced rather than repaired. Do not attempt repairs requiring machining or welding unless specifically stated and approved by the vehicle and component manufacturer. Prior to returning the vehicle to service, make certain all components and systems are restored to their proper operating condition. ASSEMBLY (REFER TO FIG. 6) NOTE: Make certain both piston orifices are open and not clogged. Grease all o-rings, o-ring grooves and bores with a barium base lubricant. [. . . ] Remove and discard o-ring (2) from piston (8). Remove screw (11), washer (12) and diaphragm (5) from exhaust cover (10). Remove four 10-24 screws which secure exhaust cover (10) to body (7). Remove and discard inlet exhaust assembly (4) from body (7). [. . . ]